Wrasses are very interesting fish. Cirrhilabrus, Wetmorella, Paracheilinus, and Psuedocheilinus all make good inhabitants of smaller aquaria.
I do have to disagree with the notion that fishes can be added no more than 1-2 every two weeks; I added both my Triggers within a week, along with a pair of Clownfishes. I usually add my fish in groups of three, since that's how I place orders.
I have never heard of a Cardinal attacking a shrimp. Wrasses, on the other hand, are highly predatory of small crustaceans. I would sooner trust a small pelagic Trigger with shrimp than I would a Fairy Wrasse.
-Lynden